1. Field of the Invention
The present invention relates to a probe apparatus for examining electrical characteristics of an object such as a semiconductor device.
2. Description of the Related Art
As known, in production of the semiconductor device, a large number of semiconductor devices are formed on a semiconductor wafer by use of the precision photographical transcription technique, or the like, and the wafer is cut down into the respecting semiconductor devices. According to the current technique, in order to improve the productivity of the semiconductor device, the electrical characteristics of each of the semiconductor devices are examined while they are still half-complete products in the form of a semiconductor wafer, by a probe apparatus, and only those which are judged to be good in the examination are carried onto the next step, for example, packaging process.
Such a probe apparatus comprises a wafer holding table movable in X-Y-Z-.theta. directions above the wafer holding Table A probe card having probes, the number of which corresponds to that of the electrode pads of the semiconductor device, is positioned adjacent to the semiconductor device. Test examination of a semiconductor device is carried out in the following manner. A semiconductor wafer is placed on the wafer holding table, and this wafer holding table is moved such as to bring the probes, which is connected to a tester, into contact with the electrodes of a semiconductor device.
With the probe apparatus of this type, since the level of the tips of probe needles differ from one probe card to another, the level of the tips of the probe needles of a probe card must be known before the start of a test examination. Thus, the semiconductor wafer on the table is lifted a very low speed, for example 500 micrometers/second, to detect the level (contact point) where the tips of the probe needles touch on the semiconductor wafer. In this step of detecting the level of the tips of probe needles, the wafer holding table is lifted at a speed so slow from the home position (the lowest position) that it takes an extremely long time to find the contact point. To save time, the semiconductor wafer is lifted at a high speed up to a safe point where it does not yet reach the tip of the probe, and then at a low speed until it touches on the tip.
Recently, in accordance with increase in the degree of integration of semiconductor devices, the number of the electrode pads of a semiconductor device has been increased, and the pitch between neighboring pads has been narrowed. In order to follow this tendency development of a probe card 2a in which probe needles 1a are arranged substantially vertical, as shown in FIG. 2, is proceeded to achieve practical use thereof, in place of a probe card 2 in which probe needles 1 are diagonally arranged as shown in FIG. 1. However, with the probe card 2a in which the probe needles 1a are substantially vertically arranged, the tips of the probe needles will be located much (about some centimeters) lower (indicated by letter h in FIG. 2) than the case of the conventional probe card 2, when the card is fixed to the probe apparatus. Consequently, in this step of detecting the level of the tips of probe needles, the lifting distance of a wafer holding table 3 for holding a semiconductor wafer or the like must be set smaller than usual. In case where the distance is erroneously set, an object such as a semiconductor device is likely to collide with the probe needles while detecting the level of the tips of the probe needles, damaging the semiconductor wafer (object) and/or the probe card.